The rapidly increasing prevalence of AIDS has made it important to understand the aggregate economic implications of this syndrome, how patterns and costs of care and outcomes differ for patients with differing sociodemographis, clinical, and functional characteristics, and how costs are influenced by the types of care provided. It is critical that we evaluate the costs of AIDS treatment more thoroughly so that we can more accurately plan for the current and future needs of these patients. Furthermore, to the extent that certain types of high quality care are less expensive than other types of care but produce similar outcomes, this information may be helpful in convincing policy makers to develop innovative models of care. In this investigation we plan to collect and analyze information on the use and costs of medical services and outcomes for a cohort of approximately 500 AIDS patients who receive their primary care at one of three settings: a prepaid group, a municipal hospital clinic, and a group practice base at a private teaching hospital. Medical utilization will include hospital services, ambulatory services including doctor office visits, diagnostic tests, and use of AZT. long term care, home health services and services provided by informal support networks and caregivers. We will also obtain information on the indirect costs related to work disability and premature mortality. Finally, by abstracting medical records and surveying patients we will gather information on patient clinical characteristics and "stage" of illness, their health status in terms of neuropsychologic function, physical function, perceived health and social activity and their sociodemographic characteristics. Using these data we plan: to assess the direct and indirect costs for persons with AIDS: to examine whether existing staging protocols and information on patients sociodemographic, clinical (other than staging), psychosocial and functional characteristics can "perdict" the incidence of hospitalization, the use of other services, and overall costs of care; to examine these same correlates in relation to survival: and to describe changes in physical and social functioning and satisfaction for persons with AIDS.